Melonate and cyamelurate stabilizers for photographic emulsions sensitized with alkylene oxide polymers



United States Patent MELONATE AND CYAMELURATE STABILIZERS FOR PHOTOGRAPHIC EMULSIONS SENSITIZED WITH ALKYLENE OXIDE POLYMERS Norman F. Beach and Fred W. Spangler, Rochester,

N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application June 17, 1954, Serial No. 437,574

16 Claims. (Cl. 95-7) This invention relates to fog inhibiting agents and stabilizers for photographic emulsions and to photographic emulsions containing them.

It is well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developable without exposure to light. There is normally a detectable amount of the silver salt reduced during development in the areas where no exposure was given; this is commonly called fog, and sometimes called chemical fog where it is necessary to distinguish between it and the eifects of accidental exposure to radialtion; in this invention, we are not concerned with the atter.

Fog depends both on the emulsion and the conditions of development; for a given emulsion it increases with the degree of development. With constant development conditions, it tends to increase with time, temperature and relative humidity of storage conditions; it is common practice to make accelerated tests of the stability of photographic emulsions by storage at increased temperature or humidity, or both. It is, of course, desirable to have emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the whole area of the sensitive coating, but when severe, it frequently is non-uniform. Fog may also be caused by exposure to chemicals, for example, hydrogen sulfide and other reactive sulfur compounds, hyrogen peroxide vapor, and strongly reducing materials. While antifoggants and stabilizers may protect, to some extent, against such effects, it is normaly understood that an antifoggant protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both.

It is known that the effective sensitivity of photographic silver halide emulsions may be increased by adding to them derivatives of alkylene oxides such as ethylene oxide polymers having molecular weights of 300 or more. The practical value of these compounds is severely limited by their tendency to increase fog on storage of the photographic film, especially storage at elevated temperatures and humidities. It has been found difficult to control this by the antifoggants commonly available without using quantities of antifoggant which partly neutralize the speed increase obtained from the alkylene oxide derivaves.

It is therefore an object of the present invention to provide a method for stabilizing photographic emulsions sensitized with alkylene oxide derivatives such as polyethylene oxides. A further object is to provide a means for reducing the fog produced upon keeping of emulsions so sensitized, especially emulsions stored under tropical or other adverse conditions. A still further object is to provide a means for stabilizing the speed and contrast of emulsions so sensitized. Other objects will appear from the following description of our invention.

These objects are accomplished in general by adding to the emulsion sensitized with alkylene oxide polymers, derivatives of melon and cyameluric acid, particularly alkali metal salts of hydromelonic acid and cyameluric acid. Specific examples of compounds which we may use are potassium melonate, sodium melonate, potassium cyamelurate and sodium cyamelurate.

The preparation of melon and alkali metal salts of 2,704,716 Patented Mar. 22, 1955 Hydromelonic acid Cyameluric acid The alkylene oxide polymers used to sensitize the emulsions may be of various types. The alkylene oxides from which the polymers are derived contain from 2 to 4 carbon atoms, e. g., ethylene oxide, propylene oxide and butylene oxide. The preparation of polymers from these compounds is described in Ellis, The Chemistry of Synthetic Resins (1935), pages 990 to 994. These compounds are also referred to as polyalkylene glycols and their use as sensitizers for silver halide emulsions is described in U. S. Patents 2,423,549 and 2,441,389.

Various derivatives of alkylene oxides may also be used to sensitize the silver halide emulsions, e. g., condensation products of alkylene oxide with glycols, such as those having from 8 to 18 carbon atoms as described in U. S. Patent 2,240,472 and British Patent 443,559, as well as condensation products of alkylene oxides with aliphatic alcohols, aliphatic acids and aliphatic amines, that is, polyalkylene ethers, esters and amides, the preparation of which is described in U. S. Patent 1,970,578, condensation products of alkylene oxides with phenols, also described in U. S. Patent 1,970,578, and condensation products of alkylene oxides with hexitol ring dehydration products, as described in U. S. Patent 2,400,532.

In each case the polyalkylene oxide or derivative of alkylene oxide should have a molecular weight of at least 300. Condensation products of ethylene oxide with long chain alcohols should have a molecular weight of about 700; other derivatives may have a molecular weight of 1500 to 4000 or more.

The polyethylene oxide polymers used in the emulsions according to our invention may be prepared either by polymerizing alkylene oxides in the presence of glycols, aliphatic compounds containing groups having an active hydrogen, phenols, or hexitol ring dehydration products, or by reacting the polymerized polyalkylene oxide with organic acids, acid chlorides or esters, which reactions produce similar products.

The principal purpose of our invention is to provide means for maintaining the sensitivity and fog of silver halide emulsions at or close to initial optimum values under conditions of high temperature or high humidity, or both. Preferably the stabilizers and fog inhibitors which we propose to use are added to the emulsion at any stage during the process of manufacture prior to coating the emulsion. Our stabilizers and fog inhibitors may be added to the emulsion in solution in any convenient solvent not injurious to the emulsion such as water or lower alcohols.

A solution of the alkali metal salt of hydromelonic acid or cyameluric acid which we employ when added in suitable concentration before coating to unsensitized or optically sensitized silver halide emulsions usually does not appreciable affect the sensitivity and fog when measurements are made soon after coating. However, when sensitometric measurements are made after appreciable intervals of time under tropical or dry conditions of storage at elevated temperatures these compounds do stabilize speed and maintain fog at a low level. The alkylene oxide derivatives used to sensitize the emulsions may be illustrated by the following specific examples although our invention is in no way limited to the use of these specific compounds.

HOCHzCHzO CH2CH2O) nCH2 CHzOH Polyethylene oxide HOCHzCHzO CI-IzCHzO) nCH2CH2OC1'7I'I33 V Polyethylene oxide oleyl ether where n=an integer greater than about 10.

The preparation of silver halide emulsions involves three separate operations: (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of the emulsion from aqueous soluble salts usually by washing, (3) the second digestion or after-ripening to obtain increased sensitivity (Mees, The Theory of the Photographic Process, 1942, page 3). The fog inhibiting agents may be added at any stage, preferably after the final digestion.

The photographic emulsions which we use are of the developing-out type and best results have been obtained with gelatino-silver bromoiodide emulsions. However, emulsions of varying halide content may be used.

The emulsions may be chemically sensitized by any of the accepted procedures, in addition to or in combination with the sensitizing with alkylene oxide polymers. The emulsions may be digested with naturally active gelatin, or sulfur compounds may be added such as those described in Sheppard U. S. Patent 1,574,944 and 1,623,499, and Sheppard and Brigham U. S. Patent 2,410,689. The emulsions may also be treated with salt of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum, all of which belong to group VIII of the periodic table of elements and have an atomic weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitiz: ing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U. S. Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith U. S. Patents 2,566,245 and 2,566,263.

The emulsions may also be chemically sensitized with gold salts as described in Waller and Dodd U. S. Patent 2,399,083, or stabilized with gold salts as described in Damschroder U. S. Patent 2,597,856 and Yutzy and Leermakers U. S. Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions may also be chemically sensitized with reducing agents such as stannous salts (Carroll U. S. Patent 2,487,850), polyamines such as diethvlene triamine (Lowe and Jones U. S. Patent 2.518.698), polyarnines such as soermine (Lowe and Allen U. S. Patent 2,521,925), or bis-(fl-aminoethyl) sulfide and its watersoluble salts (Lowe and Jones U. S. Patent 2,521,926).

The emulsions may also be stabilized with the mercury compounds of Allen, Byers and Murray U. S. application Serial No. 319,611, Carroll and Murray U. S. application Serial No. 319.612 and Leubner and Murray glgszapplication Serial No. 319,613, all filed November The sensitizing and stabilizing combinations of polyalkylene oxides and alkali metal salts of hydromelonic acid and cyameluric acid are efiective in the presence or absence of optical sensitizing dyes. Since optical sensitizing may affect stability of emulsions with respect to sensitivitv, fog and latent image changes, the action of the alkali metal melonate or cyamelurate is not completely independent of optical sensitizing or other emulsion variables. We have found, however, that both unsensitized emulsions and emulsions sensitized with cyanine or merocyanine dyes or both may be treated with polyalkylene oxides and alkali metal melonates or cyamelurates according to our invention.

The most useful concentration of alkali metal melonate cr'cyamelurate in the emulsion is from 0.2 to 5 or more grams per gram mole of silver halide in the emulsion. These amounts may be used in combination with one or more of the chemical sensitizing and stabilizing agents listed above.

The stabilizing action was determined by incubation of the emulsions for a period of one or two weeks at 120 F. and constant humidity. Speeds were measured in terms of ASA speeds. The results of aging tests are tabulated in the examples below and compare speed, gamma and fog of the emulsions with and without the stabilizin g compounds.

Example I A negative-speed gelatino-silver bromoiodide emulsion was digested with a sulfur compound such as disclosed in Sheppard U. S. Patent 1,574,944 and potassium chloroaurate, and chemically sensitized with about 0.65 gram per gram mole of silver halide, of polyethylene oxide oleyl ether. The emulsion was then panchromatically sensitized. To a portion of the emulsion there was added the amount of potassium melonate shown in the following table. Portions of the emulsion with and without the potassium melonate were coated on cellulose acetate film support, dried, exposed on an Eastman lb sensitometer and developed for 5 minutes at 68 F. in a developer of the following formula:

Grams N-methyl-p-aminophenol sulfate 2.5 Hydroquinone 2.5 Sodium sulfite (desiccated) 30 Sodium metaborate 10 Potassium bromide V 0.5

Water to 1 liter.

Portions of the film with and without the potassium melonate were held for 2 weeks at 120 F. and constant humidity and were then exposed and developed as indicated. The results of tests for speed. gamma and fog before and after incubation of each of the samples were as follows:

Amount Fresh Test Aiter Incubation Compound per mole Speed Gamma Fog Speed Gamma Fog G. Control... 560 71 .04 400 .64 .17 Potassium melonate 1. 75 650 68 06 560 61 .15

Example 2 The emulsion of Example 1 was treated with the amounts of potassium melonate shown in the following table and portions of the coating were incubated for one week at F. instead of two weeks. Upon exposure and development as in Example 1 and testing for speed, gamma and fog before and after incubation, the following results were obtained:

The emulsion of Example'l was treated with the amounts of potassium cyamelurate shown in the following table and portions of the coatings were incubated for one week at 120 F. Upon exposure and development as in Example 1 and testing for speed, gamma and fog before and after incubation of each of the samples, the following results were obtained:

The polyethylene oxide oleyl ether used in the examples was a condensation product of one mole of oleyl alcohol with approximately 25 moles of ethylene oxide.

Instead of incorporation in the silver halide emulsion, the fog inhibitor of our invention may be incorporated in a colloid layer such as a gelatin overcoating layer or interlayer in contact with the emulsion.

The fog-inhibiting agents which we have described may be used in various kinds of photographic emulsions. In addition to being useful in non-sensitized emulsions they may also be used in orthochromatic, panchromatic and X-ray emulsions. If used with sensitizing dyes, they may be added to the emulsion before or after the dyes are added. Various silver salts may be used as the sensitive salt, such as silver bromide, silver iodide, silver chloride or mixed silver halides. The alkali metal salts of hydromelonic acid and cyameluric acid and the alkylene oxide, etc., polymers may be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers, or emulsions to be developed by solutions containing couplers.

What we claim is:

l. A light-sensitive silver halide emulsion sensitized with an alkylene oxide polymer selected from the class consisting of 1) polyalkylene glycols, (2) condensation products of alkylene oxide with glycols, (3) condensation products of alkylene oxide with aliphatic compounds selected from the class consisting of alcohols, acids and amines, (4) condensation products of alkylene oxide with phenols, and (5) condensation products of alkylene oxide with hexitol ring dehydration products, said alkylene oxide containing from 2 to 4 carbon atoms and said alkylene oxide polymer having a molecular weight of at least 300, said emulsion containing as a fog inhibiting and stabilizing agent an alkali metal salt of an acid selected from the class consisting of hydromelonic acid and cyameluric acid.

2. A light-sensitive silver halide emulsion sensitized with an ethylene oxide polymer having a molecular weight of at least 300, said emulsion containing potassium melonate as a fog inhibiting and stabilizing agent.

3. A light-sensitive silver halide emulsion sensitized with an ethylene oxide polymer having a molecular weight of at least 300, said emulsion containing potassium cyamelurate as a fog inhibiting and stabilizing agent.

4. A light-sensitive silver halide emulsion sensitized with a polyethylene oxide oleyl ether having a molecular weight of at least 300, said emulsion containing potassium melonate as a fog inhibiting agent.

5. A light-sensitive silver halide emulsion sensitized with a polyethylene oxide oleyl ether having a molecular weight of at least 300, said emulsion containing potassium cyamelurate as a fog inhibiting and stabilizing agent.

6. A light-sensitive silver halide emulsion sensitized with a condensation product of one mole of oleyl alcohol with approximately 15 moles of ethylene oxide, said emulsion containing potassium melonate as a fog inhibiting and stabilizing agent.

7. A light-sensitive silver halide emulsion sensitized with a condensation product of one mole of oleyl alcohol with approximately 15 moles of ethylene oxide, said emulsion containing potassium cyamelurate as a fog inhibiting and stabilizing agent.

8. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with an alkylene oxide polymer selected from the class consisting of (l) polyalkylene glycols, (2) condensation products of alkylene oxide with glycols, (3) condensation products of alkylene oxide with aliphatic compounds selected from the class consisting of alcohols, acids and amines, (4) condensation products of alkylene oxide with phenols, and (5) condensation products of alkylene oxide with hexitol ring dehydration products, said alkylene oxide containing from 2 to 4 carbon atoms and said alkylene oxide polymer having a molecular Weight of at least 300, said emulsion containing as a fog inhibiting and stabilizing agent an alkali metal salt of an acid selected from the class consisting of hydromelonic acid and cyamelun'c acid.

9. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with an ethylene oxide polymer having a molecular weight of at least 300, said emulsion containing potassium melonate as a fog inhibiting and stabilizing agent.

10. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with an ethylene oxide polymer having a molecular weight of at least 300, said emulsion containing potassium cyamelurate as a fog inhibiting and stabilizing agent.

11. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with a polyethylene oxide oleyl ether having a molecular weight of at least 300, said emulsion containing potassium melonate as a fog inhibiting and stabilizing agent.

12. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with a polyethylene oxide oleyl ether having a molecular weight of at least 300, said emulsion containing potassium cyamelurate as a fog inhibiting and stabilizing agent.

13. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with a condensation product of one mole of oleyl alcohol with approximately 15 moles of ethylene oxide, said emulsion containing potassium melonate as a fog-inhibiting and stabilizing agent.

14. A light-sensitive sulfur-sensitized silver halide emulsion additionally sensitized with a condensation product of one mole of oleyl alcohol with approximately 15 moles of ethylene oxide, said emulsion containing potassium cyamelurate as a fog-inhibiting and stabilizing agent.

15. The emulsion of claim 13 which is additionally chemically sensitized with gold salts.

16. The emulsion of claim 14 which is additionally chemically sensitized with gold salts.

No references cited. 

1. A LIGHT-SENSITIVE SILVER HALIDE EMULSION SENSITIZED WITH AN ALKYLENE OXIDE POLYMER SELECTED FROM THE CLASS CONSISTING OF (1) POLYALKYLENE GLYCOLS, (2) CONDENSATION PRODUCTS OF ALKYLENE OXIDE WITH GLYCOLS, (3) CONDENSATION PRODUCTS OF ALKYLENE OXIDE WITH ALIPHATIC COMPOUNDS SELECTED FROM THE CLASS CONSISTING OF ALCOHOLS, ACIDS AND AMINES, (4) CONDENSATION PRODUCTS OF ALKYLENE OXIDE WITH PHENOLS, AND (5) CONDENSATION PRODUCTS OF ALKYLENE OXIDE WITH HEXITOL RING DEHYDRATION PORDUCTS, SAID ALKYLENE OXIDE CONTAINING FROM 2 TO 4 CARBON ATOMS AND SAID ALKYLENE OXIDE POLYMER HAVING A MOLECULAR WEIGHT OF AT LEAST 300, SAID EMULSION CONTAINING AS A FOG INHIBITING AND STABILIZING AGENT AN ALKALI METAL SALT OF AN ACID SELECTED FROM THE CLASS CONSISTING OF HYDROMELONIC ACID AND CYAMELURIC ACID. 